.TH std::basic_ifstream::is_open 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::basic_ifstream::is_open \- std::basic_ifstream::is_open

.SH Synopsis
   bool is_open() const;

   Checks if the file stream has an associated file.

   Effectively calls rdbuf()->is_open().

.SH Parameters

   \fI(none)\fP

.SH Return value

   true if the file stream has an associated file, false otherwise.

.SH Example


// Run this code

 #include <fstream>
 #include <iostream>
 #include <string>

 // this file is called main.cpp

 bool file_exists(const std::string& str)
 {
     std::ifstream fs(str);
     return fs.is_open();
 }

 int main()
 {
     std::boolalpha(std::cout);
     std::cout << file_exists("main.cpp")  << '\\n'
               << file_exists("strange_file") << '\\n';
 }

.SH Possible output:

 true
 false

   Defect reports

   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.

     DR    Applied to             Behavior as published              Correct behavior
   LWG 365 C++98      is_open was not declared with const qualifier declared with const
                                                                    qualifier

.SH See also

   open  opens a file and associates it with the stream
         \fI(public member function)\fP
   close closes the associated file
         \fI(public member function)\fP
